1. Field of the Invention
The present invention relates generally to pull type crop harvesting machines particularly, although not exclusively, mower conditioners in connection with which the invention will, in the main, be discussed.
In this specification "righthand", "left hand", "forward" and "rearward" references are determined by standing at the rear of the machines and facing the direction of forward travel.
2. Description of the Prior Art
It is recognised that a pull-type harvesting machine must be offset relative to the towing tractor during operation to prevent the tractor trampling the crop before it is harvested by the machine. However, for transportation on public roads, for example, the harvester should be positioned in line with the tractor and the overall width of the tractor with the harvester attached therebehind must not exceed 2.5 meters to comply with various traffic regulations. Most prior art harvesters have an angularly adjustable drawbar pivotally mounted to one side of the harvester frame and extending along one side of the header (e.g. U.S. Pat. No. 3,599,411). Power is transmitted to the harvester via a power line which is mounted on, and generally parallel to, the drawbar and which is connected to a gearbox which itself is mounted on the frame adjacent the drawbar pivot shaft and adjacent the side of the header. Because of the side-mounted gearbox and drawbar, the harvester is wider in the transport position than the harvesting width (e.g. the cutting width in case of a mower or mower conditioner). In other words, the maximum harvesting width of such machines is substantially less than the overall width.
In an attempt to overcome this disadvantage and maximise the operating width, other machines have been provided with an arched tongue or drawbar pivotally connected to the machine at a location rearwardly of the header or harvesting apparatus and capable of being swung thereover (e.g. U.S. Pat. No. 3,832,837 and U.S. Pat. No. 3,868,811). In such machines the effective harvesting width practically equals the total machine width when in the transport position. Known mower-conditioners equipped with an arched "over-the-header" tongue have a reciprocating sickle-type cutter bar and a reel structure positioned thereabove for conveying cut crop rearwardly over the cutter bar to the conditioner means. The arched tongue should be so dimensioned that it can pivot with clearance over the aforementioned reel. A substantial portion of this clearance is intended for enabling the header to be raised to its transport position at a substantial height above the ground, without the reel interfering with the arched tongue. All this dictates that the arched drawbar or tongue is a heavy structure having a heavily arched portion extending a substantial height above the ground. Due to this raised, arched drawbar, it is practically impossible to mount a mechanical power transmission on the drawbar. Instead, an expensive hydraulic transmission has had to be employed.
The header suspension of known mower-conditioners, equipped with reciprocating sickle-type cutterbar is arranged so that the header can pivot around a rearwardly located, horizontal, transverse pivot shaft. Hence such a cutterbar positioned at the forward end of the header does not remain horizontal either during floatation over ground irregularities or when the header is raised to a transport position. Instead, the cutterbar is inclined upwardly in a forward direction when the header is in a raised position. Recently, the conventional reciprocating sickle-type cutterbars of several types of harvesters have been replaced by rotary type cutters because, in general, such cutters have a much better cutting performance and a much higher operating speed.
With a rotary type cutter it is, however, essential that it remains generally horizontal during operation, irrespective of the floatation of the header in response to the rise and fall of the ground level because otherwise an uneven cut is obtained and contact with the ground may result in broken cutter blades which can be impelled by the cutters and constitute a hazard to the machine operator and others. The mower units must also preferably be held generally parallel to the ground when the header is lifted from the operative position. This means that the header suspension of a conventional harvester with a conventional reciprocating cutterbar cannot be used with a harvester employing a rotary type cutter.
There are two known types of rotary cutters, namely the so-called "disc" type and the so-called "drum" type. When a disc-type cutterbar is installed, a reel positioned thereabove is still desirable and in some structures even necessary. Hence the aforementioned disadvantage of an arched "over-the-header" drawbar being required for a pull type harvester with a maximum allowable cutting width is equally inherent in this type of harvester.
Drum-type cutters have been used in the main in mowers although some attempts have been made to combine such mowers with a crop conditioner (e.g. U.S. Pat. No. 3,751,889). However, such mower-conditioners never have been equipped with an "over-the-header" tongue or drawbar.
Most drum-type mowers have cutter drums mounted on spindles depending from a cantilevered transverse beam (e.g. U.S. Pat. No. 3,751,889). The drive for the mower units is often installed inside the beam and may comprise conical gears. This arrangement is disadvantageous as the spindles, the beam and the drive gears often are subjected to considerable loading, resulting in heavy wear in the drive and sometimes in distortion of the spindles and the transverse beam. Furthermore, gear drives are often noisy and expensive and manufacturing tolerances are tight. A lubrication system is necessary and service is difficult and frequent. Therefore, to overcome all these problems it has already been suggested to replace the gear drive by a belt drive and to support the mower units between upper and lower transverse beams. The spindles may extend through the upper beam and have drive pulleys at their upper ends above this upper beam. However, it would be better to provide the belt drive between the beams, preferably adjacent the underside of the upper beam. Unless special precautions are taken this drive arrangement would give rise to difficulties when a drive belt has to be replaced.
Known harvesting machines also incorporate assemblies for suspending the header of the machine from the machine frame. The suspension assemblies commonly include a four link system comprising pairs of upper and lower links (e.g. U.S. Pat. No. 3,751,889). These links pivotally interconnect and extend between the header and the frame. Springs usually extend between the machine frame and either the lower links or some lower part of the header itself for providing floatation of the header from the frame. While these prior art machines are generally satisfactory for their intended purposes, improvement in header suspension and floatation is desirable to enhance the overall performance and versatility of the machine under varying field conditions, such as uneven field contours or terrain. A four-link suspension system sometimes restricts lateral floatation of the header responsive to the uneven terrain or if special arrangements are made to allow the desirable lateral floatation, the construction is rather complicated and expensive. Also, when it is necessary to adjust the header tilt, two links must be adjusted by a similar amount. This is often difficult and time consuming.